High-frequency filter structure



Patented Apr. 6, 1948 meri-FREQUENCY FILTER s'rittiiiioiiii" -iirdem-QmN YQ; agisrn; erry'Corpoi-ation, a corporation of concentrictransmissi'line`device and more specifically," to low passfltes adaptedist),Inlay?n maximumV attenuation" for 'iltra' high frfrequency,-

der ofone meter'or less. This 'applicatiopwisaf division" of 'copendirigaprilication Serial l\lo,.`` 417,229; entitled Higii'fr'eqiieriejy tute"strugture, ledoctober '31; 1941, in the nar' of William Wi Hansen.

i prirent.;.from` .he speeiicatonilistenin electromagnetic energyfWavelengthofthe or; 5"'

tiQrtiiiththacq @Hammamet/ing wherein the invention isWeiggiN died inconcrete form.

Intheldraiwins., Y, Eis.; i is .a longitudinali-parti n u L im .c. :alpeL". f fii'i." In' the aboveLineriton'f application1h ther u oughan f anequivalent cirdisclosed r4an"'improved "and practicable er'ri d cuit `o`he filter i i ment of `high freqiiiieyiiute structure 'i'itiiiziii 2,1

"inv tion em voltagemay 'be applied between" the` `sect'ior1s" oi f2()said resonator.' A transiii'issio'ri linhev'ice iiri-AV i corporatingprinciples of "the preset'fiifivention may be used tolintrodce"`th"11irectionaljw voltage, 'and simultaneously to prefifit -leala'glelof ultra highfrequency"energy'fr`the ''ese- 2n nator. Suche,transmission Vline device alsomaybe A used as a lter Vtointrodcuvoltages sueltas` heater voltages, cathode voltages,V modulationvoltages, etc., through a Wallof a shieldingboxw :fm surrounding a highAfrequency' tuloe, `or other high frequency `apparatu`sf` therebypreventing any high frequency radiation fromrleaking outA of the box todisturb otherhigh frequency circuits in the vicinityo'f the shieldedtube, or for 3 other' related p'iirpo'sc-zs. a A e Therefore, aprincipalobject Aof the "presentine;V Y vention` is to provide a low'`pass yfiltersuitable for filtering out ultra high frequencies and'passuing only vunidirectional Vvoltageslsucl1g-asgarefuse'fY ful forrbeamvoltages,V heater voltagesy'QQntrol voltages, orbuncherresonatoracceleration?? voltages, or for passingverylowfrequency'modJ ulation voltages such as are .'u'sedin` ultraVAhiglilfis frequency'tube structurees'of the 'generaltypel disclosed inthe aforementioedfapplicatih .Another4 object of the preserit'invntoist'o' provide a transmission? line suitable Torj'ise such ultra highfrequncydevices," Where y u i directional `f voltages` orsuchilowrede'nqy volt ages may be appliedthrughthetransmissie line toactive'portirisffo the `iiltal,"higl'i e o quencyf devices in such amariner'thatultra hig ng..r,elat1.

frequency energy does not leak out oftli'eiltra relftuivelysmallndictosprmgs.

It will be observed from Fig. 1 Ythat the ratio of the respectiveconductor diameters Vdiiiers according to the spacing between them.Accordingly the characteristic impedance o f the respective sectionsincreases and decreases alternatelyalong the conductor, being a functionof the ratio of the inner diameter of the outerconductor to the outerdiameter of the inner conductor, thus permitting the device to operateas a transmission line for matching impedances.

It is also evident that the cross-'section of the iilter of Fig. 1 maybe revolved about any axis eccentric thereto, as shown in theapplication cf which this is a division, to generate a filter made up ofannular components. Although relative dimensions of such generateddevices may be necessarily slightly modified, they are equally useful asultra high frequency lters. Fig. 3 illustrates one such section ofrevolution, generated from Fig. 1, and made up of annular concentricportions. One portion of the section consists of inner supportingcylindrical conducting member 58, and external conducting tubular member64 secured to member 58, said member 58 being eiiectively an extensionof tubular member 64. Another portion consists of annular tubularconducting members 65 and 66 joined by reduced diameter portions 69, allof which are concentric to support 58. Tubular member65 affords lowimpedance capacitive coupling to support member 58 by virtue of theclose inter-conductor spacing, while tube 66 likewise is capacitivelylinked to external tube 64, thus again providing a closed path for ultrahigh frequency vide discontinuities in the characteristic impedance, thesuccessive sections of close spacing having progressively lowerimpedance and the successive sections of wide spacing havingprogressively higher impedance, thereby tending to increase thereliection of high frequency waves toward the source.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, itV is intended that allmatter contained in the above Vdescription orshown in the accompanyingdrawings shall be interpreted as illustrative andi not in a limitingsense. What is claimed is:

1. A high frequency lter comprising coexten sive-inner and outerconductors, means providing; a, plurality of axially separated sectionsof relatively small interconductor spacing within said'. filter, andmeans providing a plurality of axiallyi separated sections of relativelylarge intercon. ductor spacing within said filter alternating with; saidfirst sections and `being equal in length to said iirst sections, therelative interconductor.` spacing in said sections being such that saidiilter: suppresses high frequency energy and passes lows frequency andunidirectional wave energy.

2. A high frequency filter comprising coextenisive inner. and outerconductors, means providing a plurality of axially separated sectionsof." relatively small inter-conductor spacing within.; said lter, andmeans providing a plurality of;

axially spaced sections of relatively large interconductor spacingwithin said lter alternating. with said first sections, wherein saidsections aref each equal in axial length to approximately once quarterof the wavelength to be suppressed, and the relative inter-conductorspacings in said sections being such that said filter suppresses highfrequency energy and passes low frequency and current, while allowingvaunidirectional and/or a low frequency modulating voltage to betransmitted along the separate members.

Annular filter sections 69, 'III function similarly to the filter-described in Fig. 1. Filter element 10 has a hollow annular internalcavity 9|, which may be supplied with cooling water through tubes orconduits 'H and 12, which extend through end wall 'i3 and are supportedby two glass bell jar members 14 and 'I4' placed on the diameter of wall13. Heat also maybe removed by allowing a cooling fluid to ow throughaxial bore 6I in support 58.

It will be observed from Fig. 3 that the device comprises an internalmember 58 cooperating with the surrounding walls of outer members 69 andof reduced diameter portions 65 to provide an elongated chamber betweenthe members having inwardly projecting walls at spaced intervals, toprovide the same rhythmic effect as the alternate outwardly extendingsections 35 of Fig. 1. In any case the chambers 6D between therespecunidirectional wave energy,

3. The iilter defined in claim l, including solid dielectric meansinterposed between said conductors at said sections of smallinterconductor spacing.

4.A The filter dened in claim 1, including means providing passage of aIcooling iiuid interiorly of at least one of said conductors.

5. A transmission line filter device comprising arrouter conductor; asubstantially concentrically disposed inner conductor, said innerconductor having a plurality of axially separated enlarged sectionsextending radially outward from said tive members are characterized bythe opposite ter-wavelength. The cascaded sections suppress.

high frequency current, since the successively adjoining sections ofclose and Vwide spacing pro-l innerv conductor, said sections beingequal in length to the separations therebetween and having an outerperipheral surface in closely spaced relation to the inner peripheralsurface of said outer conductor; and a dielectric member interposedbetween said respective inner and outer peripheral surfaces.

6. A transmission line filter device comprisingan outer tubularconductor; an inner conductorextending substantially coaxially withinsaid tubular conductor, said conductors having a plu. rality of axiallyseparated sections providing rel..

atively close inter-conductor spacing; and having one another.

'7. A lter device comprising a tubular outer conductor; a substantiallyconcentrically disposed inner conductor, said inner conductor having aplurality of axially separated enlarged sections extending radiallyoutward from said inner conductor, each of said sections having an outerperipheral surface in closely spaced relation to the inner peripheralsurface of said tubular outer conductor; and a tubular dielectric memberlocated concentri'cally Within said device between said respectiveconductors, said enlarged sections being electrically ofquarter-wavelength along the axis of said device, and said enlargedsections being :spaced along said conductor by similarquarter-wavelengths between adjoining sections.

8. A transmission line device comprising a tubular outer conductor, aconcentric extension of said outer conductor, and a substantiallyconcentrically disposed annular inner conductor having a plurality ofaxially separated reduced diameter sections extending radially inwardtoward said extension, each or said sections having an inner peripheralsurface in spaced relation to the outer peripheral surface of saidextension.

9. A transmission line device comprising a tu bular outer conductor, anda substantially concentrically disposed inner conductor, said innerconductor having a plurality of axially separated enlarged sectionsextending radially outward from said inner conductor said sections beingequal in length to the separations therebetween, each of said sectionshaving an outer peripheral surface in closely spaced relation to theinner peripheral surface of said tubular outer conductor, at least oneof said conductors being hollow, and said device being provided withconduit means for circulating a iiuid within said hollow conductor.

10. A iilter device for suppressing high frequency radio oscillations,comprising a first hollow tubular conductor, an axial extension on saidrst conductor, and a substantially annular second conductor disposedconcentrically within said first conductor surrounding said extension ofisaid rst conductor, said respective conductors having at intervalsspaced along their axis a pluralityl of similar sections of closeinter-conductor spacing, with said sections being separated axially byportions of greater inter-conductor spacing, and said portions beingequal in length along said axis to the length of said sections.

11. A filter device as claimed in claim wherein said sections are denedby spaced inward and outward radial projections on said secondconductor.

12. An ultra high frequency filter comprising a hollow tubular outerconductor, a concentric inner conductor, a plurality of spaced radially6 enlarged conductive members, equal in length to the separation'therebetween, on said inner conductor, and a sleeve of dielectricmaterial inter posed between the outer peripheries of said conductivemembers and the inner periphery of said outer conductor.

13. An ultra high frequency iilter comprising a hollow tubular outerconductor, a concentric inner conductor, hollow radially enlargedportions on said inner conductor spaced along said conductor `byseparations equal in length to said portions, each of said portionshaving the outer periphery thereof adjacent to and coextensive with partof the inner periphery of said outer conductor, and means providing forpassage of cooling fluid through said hollow inner conductor portions.

14. The filter deiined in claim 13, wherein said outer conductor isprovided wvith an axial extension, and said hollow inner conductorportions are substantially annular and surround said extension.

15. The lter defined in claim 13, wherein said outer conductor isprovided with an axial extension, and said hollow inner conductorportions have the inner and outer peripheries thereof respectivelyadjacent to and coextensive with parts of the outer periphery of saidextension and the inner periphery of said outer conductor.

16. A transmission line filter device comprising a tubularA outerconductor having a coaxial reentrant extension and an inner conductorconcentrically disposed therebetween, said inner conductor having yaplurality of axially separated sections spaced along said innerconductor and extending radially therefrom, the separations between saidsections being equal in length to the length of said sections, each ofsaid radially extending sections having a peripheral portion thereof inclose proximity to the inner periphery of said outer conductor and theouter periphery of said reentrant extension.

WILLIAM W. HANSEN.

REFERENCES lCITED The following references are of record in the file ofthis patent:

, A UNITED STATES PATENTS Certificate of Correction Patent No.2,438,913. April 6, 1948.

WILLIAM W. HANSEN It is hereby oertied that errors appear in the printedspecification of the above numbered potent requiring correction asfollows: Column 2, line 55, for the Word springs read spactngs; column4, line 70, for lenth read length; and that the said Letters Patentshould be read With these corrections therein that the same may conformto the record of the oase in the Patent Office.

Signed and sealed this 1st day of June, A. D. 1948.

THOMAS F. MURPHY,

Assistant 00m/mission of Patents.

